Many oil wells are produced utilizing gas pressure. The use of a gas drive for producing oil is particularly prevalent in deep wells, because deep wells cannot be practically produced by the sucker rod pump method. Thus, where water flood techniques are ot applicable, gas pressure is the only practical means to force the oil up the producing tubing. In some cases, the naturally occuring gas pressure within the strata is sufficient to force a slug of oil through the producing tubing. However, as the propelling gas and oil move upward in the producing tubing, they encounter pressure and temperature changes that permit the gas and oil to separate into two distinct phases. In such wells, the slug of oil is followed by a relatively long duration gas discharge. The discharge of gas without oil is an inefficient use of the natural gas pressure and dissipates the gas pressure before the formation has been fully produced. If the well is sufficiently deep, it may be necessary to cap the well even though large quantities of oil remain in the formation. In some caes, it is possible to add large quantities of gas to the natural formation by pumping the gas down a second well that penetrates the formation. However, the gas must be injected at high pressure. The weight of gas in the drill string adds to the original pressure to produce a total pressure that may exceed the strength capabilities of the injecting well. Further, other factors, such as porosity of the strata, may make such injection in a second well impractical.
Therefore, it is desirable to have a gas drive oil well pumping system that enhances the lifting power of gas by minimizing the separation of the gas and oil into distinct phases. Such an oil well pumping system is particularly desirable where it provides a means of injecting gas into the producing well casing at relatively low pressures to directly lift the gas in stages.